Moving IsUsingDepthTesting from CCWindow to CCLayer:
Moving IsUsingDepthTesting from CCWindow to CCLayer:

* potentially users may want to toggle depth test when drawing different layers
* CCLayer modification was fused into previous commit

mono/CocosSharp,TukekeSoft/CocosSharp,TukekeSoft/CocosSharp,MSylvia/CocosSharp,zmaruo/CocosSharp,MSylvia/CocosSharp,hig-ag/CocosSharp,hig-ag/CocosSharp,zmaruo/CocosSharp,mono/CocosSharp,haithemaraissia/CocosSharp,haithemaraissia/CocosSharp